Magnetic sound reproducer having removable stylus assembly



Patented Feb. 27, 1951 MAGNETIC SOUND REPRODUCER HAVING REMOVABLE STYLUS ASSEMBLY Norman C. Pickering, Rockville Centre, N. Y., as signor to Pickering Associates, Inc., Oceanside, N. Y., a corporation of New York Application May 7, 1949, Serial No. 91,926

3 Claims.

This invention relates to an improved armature and a removable stylus assembly for use in a magnetic sound reproducer.

It is a particular object of the invention to provide an armature of the above character for use in a magnetic sound reproducer in which the stylus is removably mounted so that it can be readily replaced when it is broken or for any other reason when it is desirable to substitute another type of stylus, but in which the stylus is rmly held in place against accidental displacement and in a manner to prevent undesirable movement with respect to the armature.

A further object is to provide, in a combination of the above type, a spring or mechanical filter which serves as a replaceable stylus holder and at the same time permits the stylus to vibrate at extremely high frequencies' without exciting the armature whereby undesirable frequencies resulting from surface irregularities in the record are eliminated.

A further object is to provide a combined mechanical iilter and removable stylus holder for use with an armature of a magnetic sound reproducer in which the filter and holder is made of non-magnetic material so as not to affect the magnetic flux of the system.

Other objects will, of course, be apparent from the following description of the drawing in which- Fig. l is a bottom plan view of a magnetic sound reproducer, with a portion of the casing` removed, embodying my improved armature and removable stylus assembly;

Fig. 2 is a longitudinal sectional view on the line 2--2 of Fig. 1; n

Fig. 3 is a perspective view of the lower portion of the armature showing the stylus assembly being inserted therein by means of a simplied holding tool;

Fig. 4 is a partially sectional view of the lower portion of the armature showing the stylus assembly supported therein;

Fig. 5 a sectional View in the direction of the arrows on thev line 5-5 of Fig. 4; and

Fig, 6 is a partially sectional View at right angles to Fig. 4 of the lower portion of the armature with the stylus assembly supported therein and showing the tool as still applied to the stylus holder.

My improved armature is illustrated generally at it and comprises a tubular member made of magnetic material having my improved combined stylus assembly il frictionally engaged with the lower portion thereof. My armature and stylus assembly may be used with any type of sound reproducen For purposes of illustration I have shown it as incorporated in a sound reproducer of the type described in my copending patent application Serial No. 681,800 filed July 8, 1946, now Patent No. 2,538,164, issued January 16, 1951.

Referring to Figs. 1 and 2, this reproducer consists of a casing l2, a permanent magnet I3 extending between the projected ends of pole pieces I4 and l5 and a current generating element in the form oi coil I positioned between but insulated from the pole pieces. The coil has a central opening l1 and the ends of the pole pieces project outwardly as shown forming a gap in the magnetic circuit in alignment with the cen.- tral opening of the coil. The two ends of the winding of coil i6 are connected by suitable leads I8 to terminal prongs I9 which can be connected in the usual manner to an amplifying and loud speaking system.

The moving system inthe illustrated magnetic sound reproducer comprises my improved armature having the removable stylus assembly supported at one end and mounted at its upper end near the free end of the cantilever spring 20 which, in turn, is mounted on. frame piece 2l. The illustrated arrangement is suitable for use with lateral cut records, In operation the stylus is displaced laterally by the modulations of the record groove and the armature in turn is caused to move towards one or the other pole pieces. This causes a ux in the armature which cuts the coil and causes electrical impulses or voltages therein which are translated into sound by the amplifying and loud speaking system. As previously stated, the particular sound reproducer shown and described herein is merely illustrative.

My present invention is concernedy primarily with the armature and replaceable stylus assembly. As previously stated, the armature should be made of a magnetic material, preferably an alloy of iron and nickel in which the nickel content ranges between and 60% by weight. I have found that in an armature of this composition the magnetic flux if almost directly proportional to the magnetic forces applied thereto throughout the normal effective range of operation. In this connection the alloy in the armature is preferably in a relatively soft state or condition in order to obtain the most accurate translation. The upper portion of armature l0 isk preferably in the form of al cylindrical tube as shown at 2| whereas the lower portion, serving as a removable holder for the stylus assembly, is in the form of a relatively flattened sleeve or displacement.

socket 22 whose broadest or widest dimension tapers slightly from its lower to its upper end as shown most clearly in Fig. 6.

The stylus assembly Il consists generally of a jewel stylus 23 retained in a holder 24 in a well-known manner by means of an eyelet or grommet 25 inserted in an aperture in the holder. The holder 2li is in the form of a spring providing vertical compliance for the stylus and serving as a mechanical filter eliminating high frequency vibrations caused by irregularities in the record surface. The spring preferably takes the form of a strip of suitable spring material, preferably non-magnetic, and for this purpose I prefer to use beryllium copper. Beryllium copper has high tensile strength and high fatigue value and forms a spring having a high stiffness to mass ratio. However, it should be understood that other spring materials may also be employed.

The stylus 23 is preferably mounted near the outer end of the spring as shown. The opposite end of the spring is preferably formed with a projecting tongue 2G extending substantially at right angles to the spring. The upper end of the tongue 26 preferably tapers rather sharply as shown at 2l so as to facilitate its insertion into the retaining sleeve 22 at the lower end of the armature. The lower or main body portion of thev tongue is formed with a slight taper corresponding to the taper of sleeve 22. Likewise the width of the tongue 26 corresponds with the internal width of the retaining sleeve 22 so that when the tongue is inserted in the sleeve in the manner illustrated in Figs. 4, 5 and 6 it fits snugly therein and is retained firmly in place against undesirable movements, particularly in a lateral direction, with respect to the armature. In this manner all lateral movements of the stylus in response to modulations of the record groove are transmitted to the armature. On the other hand, the lter spring 24 permits compliance of the stylus in a vertical direction eliminating the undesirable frequencies resulting from surface irregularities.

When the stylus assembly is inserted rmly in place in the retaining sleeve of the armature it is frictionally held in place against accidental On the other hand, when desired, the tongue can be removed from the sleeve thereby permitting replacement of the stylus assembly. If, through inadvertence when the stylus assembly is replaced, the tongue is not forced all the way home in the sleeve, vibration will drive the tongue all the way home and due to the wedging action resulting from the tapering fit the stylus assembly will then be held firmly in place transmitting all lateral movements of the stylus to the armature.

It will be appreciated that the stylus assembly can be readily replaced either manually or by means of a simple tool. In Figs. 3 and 6 I have illustrated a simple tool which may also be applied to the stylus assembly in the manner illustrated for stocking and packaging purposes so `as to facilitate handling the assembly.

The tool is shown generally at 28 and comprises va handle portion 29 and a reduced upper portion having a bifurcated end 39. The bifur- `cated ends are provided with confronting slots 3l of a width to frictionally engage the two sides of the spring portion of the stylus assembly and hold the assembly firmly in place in the manner of a pair of tweezers. However, the tool may be physically withdrawn from the end ofthe spring when desired. It will be seen from Figs. 3 and 6 that it is a relatively simple matter to grasp the handle 29 of the tool between the fingers and insert the tongue of the stylus assembly in the retaining socket of the armature. Thereafter, the tool is withdrawn from the forward or stylus end of the spring.

Due to the small size of the stylus assembly the tool is a convenience not only in replacing the stylus assembly but in handling it for stocking and shipping purposes.

My improved armature and stylus assembly may be used in any type of magnetic sound reproducer such as the sound reproducer' illustrated and described herein. It will thus be seen that I have provided an improved armature and stylus assembly for magnetic sound reproducers in which the stylus assembly may be readily replaced when desired but will be held firmly in place against accidental displacement. Modifications may be made in the illustrated embodiment of my invention without departing from the invention as set forth in the accompany- 'ingl claims.

I claim:

l. An armature and replaceable stylus assembly for use in magnetic sound reproducers for lateral cut records comprising an elongated tubular armature made of magnetic material, said armature being tubular throughout the greater portion of its length and having a lattened. socket with a slot-like opening therein at the lower end of the armature and extending transversely thereof and a replaceable stylus assembly comprising a spring member of relatively fiat strip stock having a stylus projecting from one of the broad sides thereof adjacent one end to provide for Vertical compliance of the stylus and formed with an integral tongue of the same fiat strip stock projecting from the opposite side of the spring member adjacent the opposite end thereof with the broad dimension of the tongue extending transversely of the spring, said tongue being in releasable engagement with the fiattened socket with the side edges of the tongue in tight engagement with the side edges of the slot-like opening, and the side edges of the tongue and slot-like spring in the socket being slightly tapered in Width from the lower to the upper end and having a wedge-like t with each other.

2. A replaceable stylus assembly for use with a magnetic sound reproducer for lateral cut records and cooperable to be supported in a relativeflat flared socket formed in the armature of the reproducer and comprising a spring member of relatively fiat strip stock, a stylus projecting from one of the broad surfaces thereof adjacent one end, said spring member providing for vertical compliance of the stylus and serving as a mechanical filter to eliminate undesirable vibrations and an attaching tongue cooperable to be inserted in the socket in the armature and made of the same flat strip stock as the spring and integrally connected thereto, said tongue being disposed at a substantial angle to the spring .and projecting from the opposite side and opposite end of the spring from the stylus and with its broad dimension extending transversely of the spring, the side edges of the tongue converging `inwardly at a slight angle from the point of attachment so that the tongue has a wedge-like fit with-the sides of the socket.

3. A replaceable stylus assembly as set forth inclaimz in which the converging angle of the side edges of the tongue increases at the free end Number thereof so as to provide an entry part for guid- 2,061,961 ing the tongue into the socket. 2,320,416 NORMAN C. PICKERING. 2,336,679 2,373,181 REFERENCES CITED 2,459,692 The following references are of record in the 214761414 fue of this patent:

UNITED STATES PATENTS m Number Number Name Date 233,841

1,682,144 Peterson Aug. 28, 1928 Name Date Culver Nov. 24, 1936 Dally June 1, 1943 Geib Dec. 14, 1943 Fleming Apr. 10, 1945 Fletcher Jan. 18, 1949 Hutter July 19, 1949 FOREIGN PATENTS Country Date Great Britain May 21, 1924 

